For proper utilization of natural or man-made fibers it is essential to have precise, accurate, and basic tensile characteristics of the fibers. To illustrate, in the making of yarn from cotton or polyester staple, in the researching genetic influences upon characteristics of cotton or wool, or in the production of man-made fibers from carbon or glass, data relating to the tensile characteristics of the fibers commonly need to be compiled and studied. As used herein, the term "tensile" will be understood to include force-elongation characteristics and cross-sectional characteristics. For example, the traditional material characteristic of tensile stress is simply the ratio of breaking force divided by cross-sectional area; common dimensions for tensile stress are pounds/inch.sup.2 or newtons/m.sup.2. As a second example, percentage elongation is commonly taken as the elongation for which Hooke's Law holds (when incremental force is directly proportional to incremental elongation) divided by the untensioned length (gauge) of the material times 100%. (Note that this definition of elongation exchanges elongation components when the force is small, i.e., "crisp" or "stack", or when force is not linear with incremental elongation.)
It is desirable that such tensile data be generated quickly and in sufficient quantities to permit the statistical analysis of the fibers.
Known instruments used for obtaining tensile data on a bundle of fibers are not capable of providing data on individual fibers. In the textile industry, it is traditional to test bundles of fibers as opposed to single fibers. In part, the rationale behind this procedure is that fibers are normally used in bundles such as in cotton yarn (thread). However, these traditional test procedures do not provide much, if any, information about the single fiber. For example, a break test of a fiber bundle will not provide much information about the amount of load each fiber bears during the test or the manner in which each fiber elongates and breaks during the test. Even if the sensitivity of the force transducer is made very high, the data obtained from a fiber bundle test is masked to some extent by damaged oscillatory response of the force transducer or ringing. That is, as individual fibers in a bundle break, a ringing oscillation is inherently set up in the test device that may distort data. Since the fibers of a bundle break at varying elongations, this ringing effect is occurring throughout the majority of the test. Ringing may not significantly affect the data as to the entire bundle, but it is usually sufficient to frustrate any attempt to derive precise data as to individual fiber characteristics or contributions.
Existing instruments for testing a single fiber, such as the Instron force-elongation tester, are very slow to use due to procedures normally involved in preparing the fiber for testing. In the textile industry, individual fiber testing is seldom done because the statistical quality of data thus obtained is not viewed as useful as bundle test data.
It is therefore a general object of the present invention to provide an apparatus and method for testing single fibers wherein data accumulated are obtained quickly and in sufficient quantities to be statistically meaningful.